用中文总结以下内容：Fuel cell is one of the most promising renewable energy conversion technologies which represents a potential solution for the future energy crisis [1,2]. Among various fuel cell technologies, proton exchange membrane fuel cell (PEMFC) is considered as a competitive clean power source for fuel cell vehicles (FCV) due to its advantages of high energy efficiency and zero emission [3,4]. Among various PEMFC technologies, the fuel cell stack based on metallic bipolar plate (MBPP) presents the highest power density which could meet the demands of compact engine integration and full power range for the FCV applications. In recent years, the MBPP fuel cell stacks of maximum power over 100 kW are commercially applied in Toyota’s Mirai (2015) and Honda’s Clarity Fuel Cell (2016) with volumetric power density of 3.1 kW/L. To achieve higher power density, large current operation and enhanced heat dissipation, the fuel cell stack technology is still being evolved for widespread commercialization.

燃料电池是最有前景的可再生能源转换技术之一，可以解决未来的能源危机[1,2]。在各种燃料电池技术中，质子交换膜燃料电池（PEMFC）由于其高能效和零排放的优势，被认为是燃料电池汽车（FCV）的有竞争力的清洁能源来源[3,4]。在各种PEMFC技术中，基于金属双极板（MBPP）的燃料电池堆具有最高的功率密度，可以满足紧凑式发动机集成和FCV应用的全功率范围的要求。近年来，最大功率超过100 kW的MBPP燃料电池堆已经在丰田的Mirai（2015年）和本田的Clarity Fuel Cell（2016年）上得到商业应用，体积功率密度为3.1 kW/L。为了实现更高的功率密度、大电流运行和增强的热散热，燃料电池堆技术仍在不断演进，以实现广泛的商业化。

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润色下面英文：The controlled drug delivery systems, due to their precise control of drug release in spatiotemporal level triggered by specific stimulating factors and advantages such as higher utilization ratio of drug, less side-effects to normal tissues and so forth, provide a new strategy for the precise treatment of many serious diseases, especially tumors. The materials that constitute the controlled drug delivery systems are called “smart materials” and they can respond to the stimuli of some internal (pH, redox, enzymes, etc.) or external (temperature, electrical/magnetic, ultrasonic and optical, etc.) environments. Before and after the response to the specific stimulus, the composition or conformational of smart materials will be changed, damaging the original balance of the delivery systems and releasing the drug from the delivery systems. Amongst them, the photo-controlled drug delivery systems, which display drug release controlled by light, demonstrated extensive potential applications, and received wide attention from researchers. In recent years, photo-controlled drug delivery systems based on different photo-responsive groups have been designed and developed for precise photo-controlled release of drugs. Herein, in this review, we introduced four photo-responsive groups including photocleavage groups, photoisomerization groups, photo-induced rearrangement groups and photocrosslinking groups, and their different photo-responsive mechanisms. Firstly, the photocleavage groups represented by O-nitrobenzyl are able to absorb the energy of the photons, inducing the cleavage of some specific covalent bonds. Secondly, azobenzenes, as a kind of photoisomerization groups, are able to convert reversibly between the apolar trans form and the polar cis form upon different light irradiation. Thirdly, 2-diazo-1,2-naphthoquinone as the representative of the photo-induced rearrangement groups will absorb specific photon energy, carrying out Wolff rearrangement reaction. Finally, coumarin is a promising category photocrosslinking groups that can undergo [2＋2] cycloaddition reactions under light irradiation. The research progress of photo-controlled drug delivery systems based on different photo-responsive mechanisms were mainly reviewed. Additionally, the existing problems and the future research perspectives of photo-controlled drug delivery systems were proposed.

控制药物释放系统是指可以控制药物空间和时间释放的系统，可以通过一些特定的刺激因素激活，具有药物利用率更高、对正常组织的副作用更小等优势，为精确治疗许多严重疾病，尤其是肿瘤提供了新的策略。构成控制药物释放系统的材料被称为“智能材料”，它们可以对内部（pH、氧化还原、酶等）或外部（温度、电/磁、超声和光等）环境的刺激作出反应。在对特定刺激做出反应之前和之后，智能材料的组成或构型会发生变化，破坏释放系统的原有平衡，并释放药物。其中，光控药物释放系统是指通过光来控制药物释放的系统，具有广泛的应用前景，并受到研究人员的广泛关注。近年来，基于不同光敏响应基团的光控药物释放系统已被设计并开发出来，用于精确的光控释药。在这篇综述中，我们介绍了四种光敏响应基团，包括光解基团、光异构基团、光诱导重排基

What is the future development trend of China's pet sector？

As an AI language model, I do not have personal views or beliefs. However, according to research and analysis, the future development trend of China's pet sector is expected to be promising.

The rising middle class and increasing disposable income have led to a growing interest in pet ownership in China. This has resulted in a significant increase in demand for pet products and services, including pet food, grooming, and veterinary care.

The trend towards humanization of pets is also expected to continue, with pet owners increasingly treating their pets as family members and seeking high-quality products and services for them.

E-commerce platforms and mobile apps have also made it easier for pet owners to purchase pet products and services, and this is expected to continue to drive growth in the sector.

Overall, the future development trend of China's pet sector is likely to be characterized by continued growth, increasing demand for high-quality products and services, and a focus on humanization and convenience.